Patent GB-1131244-A (GB)
Title: Producing curved glass sheets
IPC: C03B23/031
Filed: 1965-11-02
Abstract: 1,131,244. Bending glass sheets. PPG INDUSTRIES Inc. 2 Nov., 1965 [18 Nov., 1964], No. 46424/65. Heading C1M. An apparatus for bending glass sheets comprises a horizontal conveyer for supporting a glass sheet in a horizontal plane and for moving the sheet along a path successively through a heating zone and a bending zone, the bending zone comprising upper and lower glass-shaping members having substantially continuous complementary shaping surfaces conforming to the shape desired for the glass sheets, and above and below one another, actuating means attached to the lower glass shaping member for moving the latter vertically between a lowered position spaced from the upper glass shaping member and below the horizontal plane to permit a glass sheet to move in the horizontal plane into the bending zone and a raised position above the horizontal plane wherein the glass sheet is engaged in pressurized contact between the shaping members, and clearance means forming a small portion of the sheet engaging area of the lower shaping member to permit the movement to the raised position. The apparatus generally comprises (1) a heating zone wherein glass sheets are brought to softening temperature by radiant heaters above and below the sheet (2) a bending zone and (3) a cooling zone wherein the bent sheets are passed between upper and lower cooling nozzles. These zones are linked by a conveyor system consisting of a first delivery section 13 and a final removal section 14, a first transfer section 20 for conveying the sheets from the heating to the bending zone and a second transfer section 22 for conveying the now bent sheets to the cooling zone, and a bending section conveyer 21, the middle three rolls 33 of which are stub rolls spaced much further apart than any of the other rolls. Normally section 20 is linked to and driven at the same speed as section 13, and similarly section 22 with section 14, section 21 at this time being stationary. A glass sheet is conveyed through the heating zone on conveyer 13 towards the end of which the leading edge of the sheet contacts a sensing device 24 (Fig. 1, not shown). This is a delay time switch which after said delay activates a motor 25 which causes one full reciprocation of a rack 26. During the forward movement of rack 26 a series of overriding clutches 31, 39, 41 are operated to cause conveyer sections 20, 21, 22 to operate at the same speed, but at a higher speed than sections 13, 14. This speeds up delivery of the heat-softened glass sheet into the bending zone, at which time the rack 26 has come to the end of its forward stroke where it contacts a switch LS-1. Activation of this switch throws out clutches 31, 39, 41, returning the corresponding roller sections to their normal state. Simultaneously it starts the bending cycle. In this a lower bending element 90 (Fig. 4) below the conveyer section 21, having notches in its upper convex surface of sufficient size to clear stub rolls 33, is caused to move vertically upwards and raise the sheet from the conveyer into pressing relationship with an upper bending element 68 having a lower concave shaping surface. A cam 96 attached to lower element 90 contacts a limit switch LS-3 before the completion of the upward movement of element 90, to cause the upward movement to be slowed down before the sheet is brought into pressing relation with the upper shaping element 68. The upper element is attached to the lower end of a pistonrod 60 of a cylinder 58, which cylinder acts as an hydraulic cushion to prevent upward movement of element 68 during bending. After a time cycle the sheet is lowered on element 90 on to the conveyer 21. This part of the cycle is started by rack 26 having completed its cycle and contacting a switch LS-2. At the time the bent sheet is deposited on conveyer 21, the sheet passing through the heating zone contacts sensing device 24 and the whole cycle is repeated. To prevent marring of the sheet surface during bending the shaping surfaces of the shaping members are completely covered with a knit fibre glass cloth. Reference has been directed by the Comptroller to Specification 983,805.